The present invention relates to a wire guide for use in performing a catheterization and, more particularly to a coil spring wire guide having a movable mandril.
As described herein, the purpose of a wire guide is to aid the insertion and placement of a flexible catheter within a body blood vessel. The wire guide may be used in a procedure known as catheterization by the percutaneous entry or Seldinger technique. Employing this technique, a needle assembly including a stylet and a sharp pointed inner needle is introduced into a desired blood vessel, such as for example, the femoral artery or vein. The inner needle is then withdrawn and a coil spring wire guide is inserted through the lumen of the stylet into the blood vessel. External pressure is then applied to hold the wire guide in place while the stylet is withdrawn thereover. At this point the wire guide may either be manipulated to place the distal end in the desired body location and the catheter threaded over the wire guide to the selected area, or the catheter is threaded over the wire guide and pushed within 3 or 4 centimeters of the distal end of the wire guide, whereupon, using the wire guide as a leader, the wire guide and catheter are together advanced to the desired body location.
Anyone familiar with the body vascular system can easily appreciate that considerable manipulation is required to direct the wire guide or wire guide and catheter combination to the desired body location, due to the typically tortuous path involved. As a result, wire guides used for this purpose must be sufficiently flexible at the distal tip to permit negotiation of the desired path, yet also sufficiently rigid to resist undesirable bending or doubling back during insertion and withdrawal. Heretofore, these requirements have attempted to be met by constructing the wire guide of a closely wound coil spring having an inner opening which is solder-sealed at the proximal and distal ends. The inner opening includes a relatively stiff wire mandril which provides rigidity to the wire guide. Typically, the distal portion of the mandril terminates several centimeters short of the distal end of the wire guide. Wire guides of this type, however, exhibited problems because they were too flexible along the portion of the guide forward of the mandril and too rigid or stiff along the distal portion of the mandril.
The pertinent art dislcoses at least two types of wire guides which propose to solve the above noted problems. Wire guides of the first type provide a mandril having a taper along the distal portion so that there is a more gradual transition between the highly flexible distal tip of the wire guide and the relatively rigid non-tapered portion of the mandril. While an improvement, this type of wire guide still fails to provide the desired degree of flexibility and stiffness.
Another construction which is disclosed in catheter wire guides of the second type provides a mandril which is movable longitudinally within the opening of the wire guide. The movable mandril permits the stiffness of the distal portion of the wire guide to be varied by lengthening or shortening of the flexible portion of the wire guide. In actual use, however, movable mandrils have been found not to display the requisite ease of movement which is necessary for accurate control of the distal tip in the body.
The following patents are believed generally relevant to the apparatus of the present invention in that they disclose various designs for catheter wire guides:
______________________________________ U.S. Pat. No. Inventor ______________________________________ 3,452,740 Muller 3,612,058 Ackerman 3,437,103 Cook 3,789,841 Antoshkiw 4,080,706 Heilman 4,005,369 Heilman ______________________________________
U.S. Pat. No. 3,452,740 to Muller discloses a spring guide manipulator and wire guide therefor, the wire guide being an example of a helically wound wire guide with a flexible distal tip. The wire guide does not include a moveable mandril.
U.S. Pat. No. 3,612,058 to Ackerman discloses a further example of catheter stylet or wire guide having a helically wound wire and a tubular stiffening portion or mandril disposed axially along all but the distal most tip portion of the helically wound wire. The tubular stiffening portion is not axially movable in the wire guide.
U.S. Pat. No. 3,547,103 to Cook discloses an example of a coil spring wire guide for a catheter falling within the first type. The wire guide includes a tapered mandril which is soldered to the proximal end of the wire guide and terminates short of the distal end of the wire guide. The mandril is not longitudinally movable in the wire guide.
U.S. Pat. No. 3,789,841 to Antoshkiw discloses a disposable wire guide of the first type which includes a Teflon jacket coating the non-tapered portion of the core wire. The core wire is, however, not longitudinally movable within the wire guide.
U.S. Pat. No. 4,003,369 and U.S. Pat. No. 4,080,706 to Heilman et al. disclose a further example of a coil spring wire guide of the first type in which the coil spring wire is coated with Teflon prior to winding. These patents also do not disclose a movable mandril or core wire.
There exists a distinct need for a catheter wire guide having the requisite degree of flexibility and stiffness, yet which also avoids the disadvantages associated with previous designs for catheter wire guides.